When I do this: std::vector<int> hello; Everything works great. However, when I make it a vector of references instead: std::vector<int &> hello; I get horrible errors like error C2528: ‘pointer’ : pointer to reference is illegal I want to put a bunch of references to structs into a vector, so that I don’t have to … Read more
How do I convert a std::vector<double> to a double array[]? 10 Answers 10
I have a vector of numbers: numbers <- c(4,23,4,23,5,43,54,56,657,67,67,435, 453,435,324,34,456,56,567,65,34,435) How can I have R count the number of times a value x appears in the vector? 20 Answers 20 You can just use table(): > a <- table(numbers) > a numbers 4 5 23 34 43 54 56 65 67 324 435 453 456 … Read more
How to check if a vector contains a given value? 7 s 7
I have a std::vector<int>, and I want to delete the n’th element. How do I do that? std::vector<int> vec; vec.push_back(6); vec.push_back(-17); vec.push_back(12); vec.erase(???); 16 s 16 To delete a single element, you could do: std::vector<int> vec; vec.push_back(6); vec.push_back(-17); vec.push_back(12); // Deletes the second element (vec[1]) vec.erase(std::next(vec.begin())); Or, to delete more than one element at once: … Read more
I can create an array and initialize it like this: int a[] = {10, 20, 30}; How do I create a std::vector and initialize it similarly elegant? The best way I know is: std::vector<int> ints; ints.push_back(10); ints.push_back(20); ints.push_back(30); Is there a better way? 29 s 29 If your compiler supports C++11, you can simply do: … Read more
Why is Java Vector considered a legacy class, obsolete or deprecated? Isn’t its use valid when working with concurrency? And if I don’t want to manually synchronize objects and just want to use a thread-safe collection without needing to make fresh copies of the underlying array (as CopyOnWriteArrayList does), then is it fine to use … Read more
All I want to do is to check whether an element exists in the vector or not, so I can deal with each case. if ( item_present ) do_this(); else do_that(); 17 s 17 You can use std::find from <algorithm>: #include <algorithm> #include <vector> vector<int> vec; //can have other data types instead of int but … Read more
This question already has answers here: Concatenating two std::vectors (26 answers) Closed 6 years ago. Assuming I have 2 standard vectors: vector<int> a; vector<int> b; Let’s also say the both have around 30 elements. How do I add the vector b to the end of vector a? The dirty way would be iterating through b … Read more
How do I concatenate two std::vectors? 26 s 26 vector1.insert( vector1.end(), vector2.begin(), vector2.end() );